The invention relates to a method for assembling in a precise position a planetary gear unit which comprises a planetary gear, a planet shaft with pegs on the front sides, a bearing inserted between planet shaft and planetary gear, two thrust washers and two guide washers and is to be used in a planetary transmission having one sun gear and at least one ring gear.
Many problems posed in the driving technology such as in motor vehicle transmissions demand the implementation of extreme ratios. Planetary transmissions are especially well suited to combine high ratios with a compact construction. As example of this let there be cited the so called Wolfrom coupling transmission which, at a high ratio, has great efficiency. As Wolfrom transmission is designated a specially simple coupling transmission. The drive shaft is connected with a sun gear which interacts with a planetary gear block. The planetary gear rests on an internally toothed ring gear which is fixedly connected with the housing, the web following idly as planet carrier. The movement is relayed via the planet carrier and the planetary gear is designed, for example, as stepped planet. The planetary gear meshes for its part again with a second internally toothed ring gear which forms the output.
Such a planetary transmission is adequate for a compact design which makes a great transmission densities on narrow space possible.
Especially in the handling technology, a transmission of high ratios is needed for power transmission of high speed prime movers. These transmissions must have small torsional play during load direction change. They must further stand out by a torsion-proof, light and compact design.
The Applicant""s DE A 195 10 499 has disclosed a planetary transmission having a driven sun gear, a first and a second respectively internally toothed ring gears of which the first is fixedly and the second can be notably driven and forms the output and having planetary gears supported upon axles that extend inclined in a planet carrier so as to be constantly meshed with the sun gear and the ring gear. The planetary gears are designed as stepped planets with small and large stepped gears, the toothings of the stepped gears having different modules.
The Applicant""s DE A 43 25 295 has made known one other planetary transmission with a driven sun gear and two internally toothed ring gears. In the planetary transmission, the axles supported on planetary axles in the planet carrier are disposed inclined forming an acute angle with a central axle of the planetary transmission. The planet carrier which, here follows idle, is supported with low friction upon a bushing via a ball bearing, the bushing abutting at one end, via a shoulder, on a ball bearing for adjusting the axial position of the planet carrier and, via a guard ring, can be fixedly fastened on a spacer disc.
Hereby is provided a planetary transmission free of play in which the precision is great that can be achieved in the production, which forms the basis for a tight play adjustment.
An essential part of a planetary transmission is the above mentioned planetary gear unit consisting of a planetary gear, a planet shaft, for example, with pegs on both front sides, a bearing inserted between the planet shaft and the planetary gear, two thrust washers and two guide washers and which serves for use in the planetary transmission. During the production process, there have to be made precise position planet holes with special precision spindle machines, the holes having to be processed first by prior spindling and thereafter by finishing spindling. A very high expenditure is needed to meet the tolerance requirements relative to axle inclination, axle offset, diameter tolerance and uniform cord volume. This means a great investment for special precise spindling machines, the preparation of expensive tools for the prior and finishing spindling the use of which demands considerable time, the same as the subsequently required removal of ridges and the subsequent test step. In order to ensure steps that guarantee high quality in the production process, a high production cost is accordingly needed, particularly of automatic transmission for motor vehicles.
The problem on which this invention is based is to proposed, for assembly with position precision a planetary gear unit mentioned above, a method with which the production can be carried out in a single reshaping working cycle.
On the basis of a method of the kind specified above, said problem is solved by the features stated in the claim.
According to this invention, it is proposed that the reshaping working cycle comprises the following steps:
the planetary gear unit is inserted via the ring gear and the sun gear in mean position tolerance, aligned and braced in a tool;
the tool, which has two stamps displaceable coaxially to the planet shaft and opposite to the two front sides thereof and two jaws with indented rings which jaws surround the stamps in the form of a ring and can be displaced independently of the stamps, closes until the indented rings abut on the guide washers and clamp them;
the tool closes further until the indented rings exert a constant pressure upon the outer sides of both guide washers; and
the stamps are pressed against the ends of the planet shaft with a force such that they are forged and thereby connect with position precision, positively and without play the appertaining guide washers with the planet shaft.
By virtue of this reshaping working cycle practicable in several steps, no precision spindling is needed any more for producing planetary holes. The planetary holes are here stamped during the precision stamping of the guide washers with play (of about 0.3 mm) relative to the planet shaft pegs.
The inventive simple reshaping working cycle results in a considerable reduction of cost with, at the same time, quality improvement with regard to contact pattern and noises. The planet shafts absorb part of the torque so that the planet carrier becomes more rigid. Depending on the utilization (that is, the required torque), it is completely possible to omit the planet spiders whereby a further saving in cost and weight is made possible.
The distance in the area of the planetary gears is exactly maintained by the shoulders of the planet shaft whereby an improvement in quality is achieved compared to the conventional planetary gear units; besides, the thrust washers do not have any more to be surface ground. The required investments in machines are correspondingly small in new projects.